Apparatus for measuring and indicating fluid pressure across a fluid restriction



United States Patent inventor Appl. No. Filed Patented Assignee CarlBloom Springfield, Mass.

April 3, 1968 Division of Ser. No. 491,223, Sept. 29, 1965, Patent No.3,413,855.

Dec. 15, 1970 Worthington Corporation Harrison, NJ.

a corporation of Delaware. by mesne assignments APPARATUS FOR MEASURINGAND INDICATING FLUID PRESSURE ACROSS A FLUID RESTRICTION I Claim, 2Drawing Figs.

U.S. Cl

Int. Cl

[50] Field of Search 137/560, 565. 557, 625.4; 73/389, 396, 420. 38; 116/( inquired), 70

Primary ExaminerWil1iam R. Cline Attorney Daniel H. Bobis ABSTRACT: Adevice for selectively measuring on a single gauge the pressure upstreamand downstream of an oil separating device disposed in a compressordischarge line to enable comparisons of the pressures on opposite sidesof the oil separating device and to provide accurate means fordetermining the pressure drop across the oil separating device.

PATENTED am 51970 $547,149

CARL BLOOM INVENTOR.

BY 5MMM CROSS REFERENCES TO RELATED APPLICATIONS This is a division ofapplication Ser. No. 491,223, filed Sept. 29,1965 and issued Dec. 3,1968 as US. Pat. No. 3,413,855.

SUMMARY OF THE INVENTION This invention relates generally to fluidcarrying systems, and more particularly, to apparatus in combinationwith the fluid carrying lines in such systems for measuring the pressureat fixed points in said lines and indicating the difference tn pressurebetween said fixed points and the change in pressure across an existingrestriction to fluid flow in said fluid carrying lines, whichrestriction may from time to time be subject to change in the total areaof the fluid flow opening during the operation of said systems.

In a system for carrying fluids, as for example an oil or gas pipelinesystem, or a portable compressor system, it is often desirable to placefilters in the fluid carrying lines at various points, to extract dirtparticles, and for other well known reasons.

Such filters, and other devices which produce a restriction in the fluidcarrying lines, have a greater-fluid pressure on their upstream side,than on their downstream side. This difference in pressure which is dueto friction loss and reduction in the total flow area can be measuredand is referred to as differential pressure."

If the filter, or other fluid restriction, develops an increasedresistance to fluid flow, the differential pressure or pressure drop"across said filter or fluid restriction, will also increase. Thus, in anoil pipeline system, when the oil filter, through continued use,extracts more and more dirt particles from the oil passing through it,the resistance of the oil filter to the oil flow will increase, causinga corresponding increase in differential pressure" across the oilfilter.

In prior art devices this differential pressure has been measured by twoseparate gauges; an upstream pressure gauge, and a downstream pressuregauge.

Measuring the upstream and downstream pressures by means of separategauges is inaccurate. To obtain accurate readings, the gauges wouldfirst have to be compared with one another. This comparison would haveto proceed on two fronts. First, a reference point would have to beestablished at zero flow. Second, the gauges would have to be calibratedwith respect to one another. This is cumbersome, impractical and oftenimpossible to accomplish while the system is operating, because, first,in many systems where some discharge fluid is always bled to operatecontrols, the condition of zero flow cannot be obtained, and second, atwo-gauge system requires periodic recalibration of the gauges withrespect to one another.

Of course, prior art devices which merely indicate the existence ofpressure changes without measuring their value, would be of little usein systems where the actual values of pressures and pressure changes areimportant.

Assuming that in normal operation the resistance in the filter or otherfluid restriction is small enough to permit maintenance of apredetermined downstream pressure, then a drop in such downstreampressure, unaccompanied by a corresponding drop in upstream pressure,would be indicative of an increase in the resistance of the filter orrestriction.

The present invention is particularly adaptable in such systems toindicate that the filter should be changed, and overcomes the problemspresented by the prior art devices.

Thus, the present invention covers a means in a fluid carrying systemhaving a line with a fluid restriction therein comprising, a device inthe line disposed across the restriction with a single gauge therein; tomeasure and indicate the pressure downstream of said fluid restriction;to measure and indicate the pressure upstream of said fluid restriction;and to enable one to determine the value of the pressure drop across thefluid restriction.

Accordingly, an object of this invention is to provide a means forselectively indicating and measuring the upstream and downstreampressures on either side of an in-line fluid restriction.

Another object of this invention is to provide an improved fluidpressure measuring means, which means in itself is capable of accuratelyand easily indicating the pressure drop across an in-line fluidrestriction.

Various other objects and advantages will be apparent from the followingdescription of one embodiment of the invention.

IN THE ACCOMPANYING DRAWINGS FIG. 1 is a schematic representation of arotary compressor installation having attached thereto an apparatus formeasuring the pressure drop across an in-line restriction; and

FIG. 2 is a schematic representation of said apparatus and saidrestriction.

In the illustrated embodiment of the invention as shown in FIG. 1, thecompressor 1 may be of any conventional type. It discharges through aconduit 2 into a fluid receiving tank 3, which again may be of anyconventional type, including a multifluid tank, e.g. an air oil tank.Fluid is discharged from this tank through a line 4 to the upstream sideof fluid restriction S, which can be a filter, or, in the case ofparticular portable or industrial compressors, a demister, and afterpassing through the filter is discharge in line 6 downstream of thefilter and thence through the system.

Fluid pressure discrimination means 9 is shown shunting the fluidrestriction 5 by means of first and second inlet conduits 7 and 8respectively.

The discrimination means is shown in expanded schematic in FIG. 2,wherein 10 is a control means, e.g. a three-way valve, and 11 is anindicating and measuring means, e.g. a gauge.

The valve 10 comprises a housing 12 with a fluid flow passage 13therein, first and second inlet ports 14 and 15 respectively, anddischarge port 16, for the introduction and egress respectively offluids therethrough, and chamber means 17 for coaction with actuatingmeans 18 in order to selectively restrict the flow of fluid from one orthe other inlet ports to the discharge port.

Actuating means 18 comprises internal element 19 which is slidablymounted in chamber means 17 and which is capable of sealing off theflow' of fluid from either of the first and second inlet ports 14 and15, movable mounting means 20 which is movably mounted in housing 12 andis effectively sealed, in any conventional manner, to prevent the flowof fluid from the chamber 17 between it and the housing 12, and externalimpulse means, e.g. push button 21, connected to a source of potentialenergy, e.g. spring 22, which serves to actuate the actuating means byproviding a means for receiving and transmitting an external force, e.g.that supplied by thumb pressure, to the movable mounting means 20,whereby the internal element 19 can be made to move from its depictedposi tion, in order to seal off inlet port 15 and simultaneously openinlet port 14; the spring 22 being an optional means of returning theinternal element 19 to its originally depicted position.

The gauge 11 is connected to the discharge port 16 by conduit 23 and isthereby made to be in fluid communication with the fluid in the system,i.e. either fluid in line 6 by way of conduit 8, second inlet port 15,flow passage 13 and chamber 17, or the fluid in line 4 by way of conduit7, first inlet port 14, flow passage 13, and chamber means 17. It isthus-possible for the gauge selectively to receive a pressure signalfrom either the upstream or the downstream side of the filter dependingon the position of the actuating means 18. The gauge is provided with anindexed dial 24 depicting the units of pressure 25 in any standardmeasure, cg. pounds per square inch (p.s.i.), and at least two hands 26and 27 which may vary in length, shape or color, and which indicate andmeasure the pressure in response to the pressure signal given aspreviously described.

' Hand 26 is not in itself responsive to pressure signals independentlyof hand 27. Hand 26 may be rotated manually by arty conventional means,e.g. by knob 29 at its pivot point 30. A typical mode of operation wouldbe to have hand 27 move hand 26 to the alternate position 28 in responseto an upstream pressure signalfromdine 4. Since the downstream fpressurein line 6 is lessthan th'is upstream pressure in line 4, fthe hand 27would return to its original position 3lupon once again receiving adownstream pressure signal. This operation ""can be very easilyaccomplished'by simply pressing on the button 21 with the thumb, therebydepressing the spring 22, and

' then releasingthethumb pressure and allowing the spring 22 to returnthe actuating means to its original position as depicted. Hand 26 wouldremain in alternate position 28 until m anually returned by knob 29 to aposition in engagement hand 27. When the valve is actuated as-justdescribed, itindicates and measures the downstream pressure and theupstream pressure.

e use of one valve provides an accuratemeasurement; and the use of onegauge with hands disposed as described easily indicates the differentialpressure.

' f course, the differential pressure could also be measured having theoperator read and note the difference between the two pressuresindicated by a single gauge needle.

' flNote the added advantage that when the three-way valve 10 .is notactuated, asin its depicted position, it normally indicates the pressuredownstream, which is of constant interest to the operator.

[,In a typical situation, an operator, noting a drop in downstreampressure to below that of the required value'for his system, will havemake a filter check. This consistsof pressing and releasing'the button21-as previously described, and observing the pressure drop acrossthe'filter. If this drop is gteater than the allowable drop for cleanfilters, he knows that the filter needs to be replaced. l

This invention also allows him to check the filter for replacement, eventhough the downstreampressure remains at an acceptable value. Thusitprovides him not only with a check against a possible detriment to theoverall system due to excessive pressure drop, but also with a checkagainst the operation of thefilter itself, i.e. as to whether itsfunctioning properly by keeping the fluid sufficiently pure.

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention, may be madeby thoseskilled in the art within the principle and scope of the invention, asexpressed in the appended claims.

I claim:

1. ln apressure-fluid system including a compressor having an inlet anddischarge outlet, a discharge line connected to said compressordischarge outlet, a receiving tank in said discharge line downstream ofsaid compressor, and a fluid filtering means in said discharge linedownstream of said receiving tank, the combination therewith of:

a. a three-port valve for selecting a point for line pressuremeasurement, having one port connected to the upstream side of saidfluid filtering means, and another port connected to .the downstreamside of said fluid filtering means, and actuating means for alternatelycommunicat ing the remaining port with the upstream side of said fluidfiltering means through the one port and with the downstream side ofsaidfiltering means through the other port; and

. a single indexed dial'gauge connected to said remaining port forindicating and measuring the upstream and downstream line pressureselected by said valve whereby the differential pressure across saidfluid filteringmeans may be determined'

